JP2009527066A - Bit detection for optical disk reading - Google Patents

Abstract

  The bit detector 203 for the optical disc reader has an interface 401 that receives the central aperture signal value from the optical disc reader 101. The interface assigns a first data value to a data bit having a corresponding central aperture signal value that is above a first threshold and data having a corresponding central aperture signal value that is below a second threshold. Coupled to a threshold detector 403 that assigns bits. These thresholds are set to provide high reliability of the assigned data values and to limit the data that results in a central aperture signal value between these thresholds to the minimum run length sequence. The run length detector 405 performs, for at least one data bit of the sequence of data bits having a corresponding central aperture signal value between the first threshold and the second threshold, run length encoding of these data bits. And a data value is assigned according to the data value of at least one data bit adjacent to the sequence. In particular, the minimum run length sequence is determined based on surrounding data.

Description

  The present invention relates to bit detection for optical disk reading, and more particularly, but not exclusively, to low complexity bit detection in an optical storage disk reading system.

  As can be seen from the popularity of storage disc formats such as CD (Compact Disc) and DVD (Digital Versatile Disc), optical discs have proven to be an efficient, practical and reliable way to store and distribute data. I came.

  Methods and techniques for detecting and correcting bit errors in optical disk reading systems are known.

  Particularly efficient techniques for detecting correct bit values in the presence of bit errors are known as Maximum Likelihood Sequence Estimation and in particular Partial Response Maximum Likelihood (PRML) bit detection. ing. In particular, the Viterbi algorithm is commonly used for data extraction from storage media such as communication systems and optical discs in the presence of media and electronic noise.

  Viterbi-based bit detection is frequently used in high-end modern optical disk systems to achieve reliable extraction of data stored on optical disks. Furthermore, Viterbi bit detection is expected to play a major role for future generations of optical storage devices. In particular, the use of Viterbi detection allows an increase in the capacity of a Blu-ray® disk system from 25 GB to 35 GB per storage layer on a 12 cm disk.

  However, such an increase in data capacity is achieved by a channel bit length scale down to 62 nm, which makes bit detection increasingly difficult due to increased intersymbol interference.

  While detection at such densities using Viterbi detectors is feasible, such detectors have considerable drawbacks in that they have long latency or processing delays.

  In particular, the Viterbi detector has a large delay between input and output and cannot be used for many purposes, and is particularly unsuitable for a data-aided feedback loop. However, data assisted feedback loops are often used in bit detectors and in reference level units that determine the reference level used by the Viterbi detector. For this reason, low complexity threshold (slicer) detectors are commonly used in such feedback loops to provide data assistance inputs to the reference level unit.

  However, the problem is that in order to increase the data capacity and reduce the channel length, the intersymbol interference is increased so that bit detection becomes increasingly difficult, and in particular the decision point aperture eye has several bit combinations. It can be closed about. For example, for a 30 GB Blu-ray disc reader, the threshold detector has a bit error rate of about 0.1, resulting in significantly reduced performance. In particular, the reference level for the Viterbi detector can be inaccurate or inappropriate, resulting in Viterbi detection failing to provide acceptable performance.

  Therefore, improved bit detection is advantageous, especially bit detection that allows reduced complexity, reduced error rate, reduced delay and / or increased performance.

  Accordingly, it is an object of the present invention to suitably mitigate, alleviate or eliminate one or more of the above-mentioned drawbacks, alone or in any combination.

  According to a first aspect of the present invention, there is provided a bit detector for an optical disc reader, means for receiving a central aperture signal value from an optical disc reader, and a first data value as a first threshold value. First means for assigning to a data bit having a corresponding central aperture signal value greater than and a second data value to a data bit having a corresponding central aperture signal value less than a second threshold; and For at least one data bit of a sequence of data bits having a corresponding central aperture signal value between the threshold value and the second threshold value and run-length encoding of these data bits and at least one adjacent to the sequence A bit detector is provided having second means for assigning a data value in response to the data value of one data bit.

  The present invention may allow a bit detector with improved performance. In particular, a bit detector may provide a reduced error rate, reduced latency, and / or reduced complexity. The bit detector may be suitable for a large capacity optical disk reading system and may allow detection of data bits with low complexity processing despite high intersymbol interference levels.

  The present invention utilizes knowledge of run-length encoding and very reliable data determination that determines data values for uncertain central aperture signal values.

  According to an optional feature of the invention, the second means is arranged to split the sequence into several minimum run length subsets and a remaining subset having several remaining data bits. The data bits in each of the subsets are assigned the same data value, and successive subsets in the sequence are assigned the opposite data value.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference.

  The minimum run length may be a fixed static minimum run length and / or may be variable and determined according to a given function or algorithm, resulting in a varying subset size. Each subset may specifically correspond to a minimum run length sequence, and the remaining subset may correspond to the number of data bits left after division into a minimum run length sequence. The remaining subset may be empty. In particular, the subset may reflect the only possible option for the data value of the data bits in the sequence that may result in a central aperture signal value between the first threshold and the second threshold.

  According to an optional feature of the invention, the second means converts from a first central aperture signal value of the first data bit of the sequence to the first data bit of the first and second thresholds. A first distance indication to a threshold closer to the central aperture signal value of the preceding preceding data bit is determined, and from the second central aperture signal value of the last data bit of the sequence, the first and second A second distance suggestion to a threshold closer to a central aperture signal value of a data bit subsequent to the last data bit of the first data bit, and the first distance suggestion and the second distance Depending on the comparison to the suggestion, the position of the remaining subset is configured to be determined at the beginning or end of the sequence.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference. Among other things, this feature allows a low complexity decision criterion for data values that reflect constraints imposed by run-length encoding and intersymbol interference characteristics.

  According to an optional feature of the invention, the second means is arranged to assign data values corresponding to data values assigned to adjacent data bits outside the sequence to the remaining subset. Is done.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference. In particular, if the remaining subset is located at the beginning of a sequence, the data value may be set equal to the data bit immediately preceding the sequence, thereby allowing a run-length sequence to start outside the sequence interval. Complete. Similarly, if the remaining subset is located at the end of a sequence, the data value may be set equal to the data bit immediately following the sequence, completing outside the interval of the sequence.

  According to an optional feature of the invention, the second means sets the data value of the first subset of the sequence to a data value opposite to the preceding data value of the data bit immediately preceding the sequence, wherein the remaining subset is It is empty, and is configured to be set when the preceding data value is different from the data value of the data bit immediately after the sequence and the number of subsets in the sequence is an even number.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference.

  According to an optional feature of the invention, the second means sets the data value of the first subset of the sequence to a data value opposite to the preceding data value of the data bit immediately preceding the sequence, wherein the remaining subset is It is configured to be set when it is empty, the preceding data value is the same as the data value of the data bit immediately after the sequence, and the number of subsets in the sequence is an odd number.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference.

  According to an optional feature of the invention, the second means divides the subset into a first subset located at the beginning of the sequence and a final subset located at the end of the sequence, and the data immediately before the sequence The same data value as the preceding data value of the bits in the first subset, the same data value as the subsequent data value of the data bits immediately after the series in the last subset, and the remaining subset is empty, the preceding data value Is different from the data value of the data bits immediately after the sequence and is configured to be assigned when the number of subsets in the sequence is an odd number.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference.

  According to an optional feature of the invention, the second means divides the subset into a first subset located at the beginning of the sequence and a final subset located at the end of the sequence, and the data immediately before the sequence The same data value as the preceding data value of the bits in the first subset, the same data value as the subsequent data value of the data bits immediately after the series in the last subset, and the remaining subset is empty, the preceding data value Is identical to the data value of the data bit immediately after the sequence and is configured to be assigned when the number of subsets in the sequence is an even number.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference.

  According to an optional feature of the invention, the first threshold and the second threshold are such that the probability of assigning an inaccurate data value is below the threshold.

This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference. This feature in particular allows reliable detection of data values outside the sequence to be used to determine reliable detection of data values within the sequence with low threshold detectability. The threshold may be lower than 10 ⁻³ , for example.

  According to an optional feature of the invention, the first threshold and the second threshold are such that a run length longer than a minimum run length of a run length code is the first threshold and the second threshold. It does not correspond to the central aperture signal value between.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference. In particular, this feature limits the possibility of data within the sequence and makes the determination of data bits outside the uncertain sequence so that accurate decisions based on run-length coding and data determination outside the sequence are practical. Enables accurate detection.

According to another aspect of the present invention, a disc reader for generating a first signal by reading an optical disc, a bit detector for an optical disc reader,
The bit detector has a means for receiving a central aperture signal value from the optical disc reader and a corresponding central aperture signal value that exceeds the first data value by a first threshold value. A first means for assigning to a data bit and assigning a second data value to a data bit having a corresponding central aperture signal value below a second threshold; and the first threshold and the second threshold For at least one data bit of a series of data values having corresponding central aperture signal values between, depending on the run-length encoding of these data bits and the data value of at least one data bit adjacent to the series A second means for assigning a data value.

  According to an optional feature of the invention, the optical disc reader further comprises a reference level unit configured to determine the first threshold in response to bit detection by the bit detector.

  This feature may improve bit detection and may allow detection of low complexity, low delay and low error rate data bits, especially in the presence of significant intersymbol interference. In particular, this feature may allow an accurate determination of the reference level, eg for MLSE bit detection, based on automatic adaptation and low complexity bit detection in the reference level unit.

  According to another aspect of the present invention, receiving a central aperture signal value from an optical disc reader, assigning a first data value to a data bit having a corresponding central aperture signal value above a first threshold, and Assigning a data value of 2 to a data bit having a corresponding central aperture signal value below a second threshold, and data having a corresponding central aperture signal value between the first threshold and the second threshold Assigning a data value to at least one data bit of a sequence of values according to a run-length encoding of these data bits and a data value of at least one data bit adjacent to the sequence; A method for detecting a bit value is provided.

  These and other aspects, features and advantages of the present invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

  Embodiments of the invention will now be described, by way of example only, with reference to the drawings.

  The following description focuses on an embodiment of the present invention applicable to an optical disc reading system using a run length limited encoding scheme with a fixed minimum run length of two data bits. However, it will be appreciated that the invention is not limited to this application and can be applied to many other systems including, for example, optical disc reading systems with longer or variable minimum run lengths.

  FIG. 1 shows an example of an optical disk reading device according to some embodiments of the present invention.

  In this example, the optical disk data reader 101 reads data from the optical disk 103. Data stored on the optical disk 103 is RLL (Run Length Limited) encoded. Data samples read from the optical disc are supplied from the optical disc data reader 101 to a maximum likelihood sequence estimator that is specifically a Viterbi bit detector 105. The Viterbi bit detector 105 uses a Viterbi algorithm to determine the data value read from the optical disc 103. The detected data is supplied to a data interface 107 that interfaces with an external device. The data interface 107 may provide an interface to a personal computer, for example.

  FIG. 2 shows the Viterbi detector 105 in more detail. The data received from the optical disc data reader 101 is supplied to the Viterbi processor 201, which performs MLSE bit detection, as is well known to those skilled in the art.

  However, in order to determine the appropriate criteria for MLSE detection, the Viterbi processor 201 needs to have the expected signal value information for a given data combination. In this example, the information is generated as a reference value by a reference level unit (RLU) 205 coupled to the Viterbi processor 201.

  The RLU provides automatic and implicit adaptation of the channel model to the system being measured by determining an average value for all possible data combinations of a given length. The reference level is considered as the average value of the signal for a given modulation bit sequence.

An example of a possible implementation of a 5-tap (considering a combination of 5 code values) RLU is shown in FIG. The (preliminary) detected modulation bit a _k is input together with the synchronized received signal d _k . For each clock cycle, 5 modulation bits are translated into a 4-bit address that points to one of 16 reference levels. Next, the reference value is, for example, RL _i (k) = (1−α) × RL _i (k−1) + α × d (k).
And updated with the value of d _k received. Where α is an appropriate filter coefficient that is typically very small (eg, about 0.01).

  It will be appreciated that in this example only 16 reference levels are considered for a combination of 5 data bits. However, due to the run length limitation commonly used in optical reading systems, the number of valid data combinations is smaller than the number of possible data combinations.

  Thus, the RLU generates a low-pass filtered or average signal value for various data bit combinations. For example, for the input sequence 11111, the RLU holds a reference value corresponding to the average signal value previously measured for the bit combination. Thus, the RLU essentially implements a channel model that shows the expected signal value output from the channel for a given bit combination. The value is automatically generated and retained as a previously obtained low pass filtered value. The reference level can thus be utilized by the Viterbi processor 201 to determine the path reference.

  However, the operation of RLU 205 is based on explicit knowledge or assumptions of the exact data value, and thus RLU 205 is coupled to a bit detector 203 that generates preliminary data bits based on the received signal. Simple threshold detection is commonly used in many conventional optical readers. However, this results in a high error rate that can be inappropriate for many applications. In particular, for large capacity discs such as 30 GB Blu-ray discs, because of the high intersymbol interference, simple threshold detection is not accurate, especially because intersymbol interference is generally high, and several data combinations For, the decision point opening (or eye) is completely closed.

  FIG. 4 illustrates a bit detector according to some embodiments of the present invention. The bit detector may in particular be the bit detector 203 of FIG. 2 and will be described with reference to the bit detector 203 of FIG.

  In contrast to conventional threshold or slicer detectors, the bit detector 203 of FIG. 4 uses two thresholds rather than using a single threshold, and the two thresholds increase the decision interval to high. The data is divided into a first data value interval of reliability, a second data value interval of high reliability, and an indefinite data interval. Data bits with corresponding central aperture signal values in the high confidence interval are assigned corresponding data values. These data values are then used with run length coding knowledge and corresponding signal values to determine the data values for the data bits in the indeterminate region.

  Specifically, the bit detector 203 has an interface 401 that receives the central aperture signal value from the optical disc data reader 101. In this example, the central aperture signal value corresponds to the HF signal value sample at the decision point for the data bit. Ideally, the instant is equal to the time of the maximum signal value for a given data bit when the noise and intersymbol interference contributions are removed. In other words, the central aperture signal value corresponds to the aperture for the HF signal or the maximum aperture of the eye. It will be appreciated that due to noise and synchronization inaccuracies, the actual timing may deviate from the optimum.

  FIG. 5 shows an example of an HF signal from a 30-Gbyte Blu-ray disc. Specifically, the figure shows the digital central aperture signal at 30 GB density after timing recovery and equalization. The central aperture signal value is indicated by “o” in this example, and the exact data value is indicated by “8”. However, as shown, using a simple conventional threshold detector with a “0” decision threshold results in an accurate bit decision, even in the absence of noise or timing inaccuracies. do not do. For example, due to intersymbol interference, sample number 11 is below the zero threshold even though the correct data value is +1.

  FIG. 6 shows examples of central aperture reference levels corresponding to various combinations of five data bits for a signal from a 30 Gbyte Blu-ray disc. The data value reflects the reference level using known data bits with accurate synchronization and no noise. As shown, there are several states where all have an average value of about 0 and there is no single threshold that can be used to determine whether the central data bit is 1 or -1. is there.

  In the bit detector 203 of FIG. 2, the received central aperture signal value is supplied to a threshold detector 403 that applies two thresholds rather than a single threshold. In particular, the threshold detector 403 assigns a first data value to a data bit having a central aperture signal value above the first threshold, and assigns a second data value to the central aperture signal value below the second threshold. Assign to the data bits you have.

The first and second threshold values are selected in this example so that the data values are assigned with high reliability. Thus, if the central aperture signal value is higher or lower than the corresponding threshold, so that the data value is assigned to a data bit, the data value is almost certainly accurate. These thresholds are thus selected to ensure that if a data value is assigned by threshold 403, the probability that the data value is in error is below a given threshold. The exact value of the threshold may depend on the particular embodiment, but may be for example 10 ⁻³ or 10 ⁻⁴ .

  In the 30 GB Blu-ray disc example of FIG. 6, the threshold detector implements a slicing level associated with state 5/6 (approximately −26) and a slicing level associated with state 11/12 (approximately +29). To do. Thus, for signal values below -26, -1 is assigned to the data bits and for signal values above +29, +1 is assigned to the data bits. The assignment of these data values is very reliable and the decision error is typically minimal.

  Further, the threshold detector 403 does not assign an explicit binary data value to data bits having a central aperture signal value between the two thresholds. These data bits are indicated as unreliable or indeterminate data bits, for example by assigning zero data values to these data bits.

  FIG. 7 shows an example of data values assigned by the threshold detector 403 for a signal from a 30 Gbyte Blu-ray disc.

  Further, the two thresholds utilized by the threshold detector are selected such that a run length higher than the minimum run length of the run length code does not correspond to a central aperture signal value between the two thresholds. Thus, only the minimum run length sequence will have intersymbol interference resulting in a central aperture signal value between the two thresholds.

  In the example of FIG. 6, the threshold values are selected so that the four states with the central aperture signal value between the threshold values do not correspond to any data series having a run length longer than the minimum run length of 2. You can see clearly.

  Thus, the output of the threshold detector 403 is one or more uncertain sequences known to have some very reliable data values and no run length longer than the minimum run length. Corresponds to a data signal having The information is supplied from threshold detector 403 to RLL detector 405 that uses the information to assign data values to an indeterminate series of data.

  Thus, the RLL detector 405 performs a run-length encoding of the data bits and at least one data bit of the unknown sequence of data bits having a central aperture signal value between the first threshold and the second threshold and the A data value is assigned according to the data value of at least one data bit adjacent to the series.

  In particular, as it is known that data bits of an uncertain sequence correspond to a minimum run-length sequence, the RLL detector 405 may determine that an uncertain sequence has several sizes that correspond to the minimum run-length. Into a subset of and the remaining subset. The remaining subset corresponds to the number of data bits remaining after the integer minimum run-length subset is determined.

  For this example of a minimum run length of 2, the sequence is empty if the remaining subset is empty (if the number of data bits in the sequence is an even number) or has a single data bit (the data bits of the sequence Is divided into data bit pairs).

  Each of the subsets corresponds to a minimum run length set and adjacent subsets must necessarily have the opposite polarity to ensure that the run length is kept at the minimum run length. Thus, the RLL detector 405 assigns data values to the subset and assigns them to the sequence such that a minimum run length criterion is maintained.

  In particular, if the remaining subset is not empty in the example corresponding to a sequence having an even number of data bits, the sequence is always a sequence of alternating polarity subsets preceded or followed by the remaining subset. (Corresponding to several I2 series).

  In this example, the central aperture signal value between the two thresholds can only be realized by alternating pairs of data bits with a single bit at the beginning of the sequence or at the end of the sequence. A single data bit becomes part of a run-length sequence that starts before or ends after the sequence and thus has the same data value as the adjacent bits outside the sequence.

  Thus, the RLL detector 405 determines whether the remaining subset should be placed at the beginning or end of the sequence. If the remaining subset (single bit) is at the beginning of the sequence, the data value is set equal to the data bit immediately preceding the sequence. If the remaining subset (single bit) is at the end of the sequence, the data value is set equal to the data bit immediately following the sequence.

  It will be appreciated that various criteria may be utilized to determine the location of the remaining subset. For example, a sequence of results for each possibility may be determined, and the corresponding central aperture signal value may be compared to select the most similar possibility to the actual central aperture signal value received. .

  In this example, the RLL detector 405 determines the distance between the central aperture signal value of the first bit of the sequence and the threshold closest to the central aperture signal value of the data bits immediately preceding the sequence. Similarly, the RLL detector 405 determines the distance between the central aperture signal value of the last bit of the sequence and the threshold closest to the central aperture signal value of the data bits immediately following the sequence. The remaining subset is then placed at the position where the distance is minimal. This is because the position is the most suitable position for a single bit.

  Thus, if the distance between the first data bit and the threshold of the preceding data bit is minimal, the RLL detector 405 determines the value of the remaining data bits that are set equal to the data value of the preceding data bit. Is set and placed at the beginning of the series. The sequence is then filled with the minimum run length subset by inverting the data values between the subsets.

  Similarly, if the distance between the last data bit and the threshold of the following data bits is minimal, the RLL detector 405 places the complete subset at the beginning of the sequence, and the previous data bit's Set the data value as the opposite of. The sequence is then filled with the minimum run length subset by inverting the data value between each subset. If the complete subset cannot be inserted any more, the remaining subset is inserted that is inverted with respect to the previous subset and has a data value equal to that of the data bits following the sequence.

  If the number of data bits in the sequence is equal to an integer multiple of the minimum run length data sequence, the remaining subset is empty. In this case, the exact number of minimum run length subsets can be inserted. However, it is not certain whether the start of the sequence is consistent with the start of the new run-length sequence.

However, this is determined to be true if:
If the number of subsets in the sequence is an even number and the data value of the data bits immediately preceding the data bits is different from the data bits immediately following the data sequence, or the number of subsets in the sequence is odd The data value of the data bit immediately before the data bit is the same as the data bit immediately after the data series.

  In this case, the sequence is composed of a minimum run length sequence starting at the beginning of the sequence, so the RLL detector 405 is opposite to the data value of the data bit immediately preceding the sequence. Insert a subset column with data values for the first subset.

If the condition is not met, ie:
If the number of subsets in the sequence is an even number and the data value of the data bit immediately before the data bit is the same as the data bit immediately after the data sequence, or if the number of subsets in the sequence is an odd number If the data value of the data bit immediately before the data bit is different from the data bit immediately after the data sequence, the data sequence starts from the part of the run-length sequence that starts outside the sequence. , And ends at the part of the run-length sequence that ends outside the sequence. In the minimum run-length example of 2, the indeterminate sequence thus starts with a single data bit that is part of a run-length sequence starting outside the uncertain sequence, End with a single data bit that is part of a run-length sequence that ends outside.

  Thus, the RLL detector 405 divides one of the subsets into a first subset located at the beginning of the sequence and a final subset at the end of the sequence. The data value of the first subset is set to be equal to the data value of the data bit immediately preceding the sequence, and the data value of the final subset is set to be equal to the data value of the data bit immediately following the sequence. .

  Thus, by utilizing the constraints imposed by the decision threshold and run length coding, the RLL detector 405 determines the data value for the uncertain sequence. The described approach can be applied to uncertain sequences of any length (including single data bits) and can be applied to any number of uncertain sequences, Will be understood.

As a specific example, for a minimum run length of 2, the RLL detector 405 may apply the following specific algorithm:
Odd number of unknown bits:
Determine the distance between the central aperture signal value of the first uncertain data and the threshold value used for the previous data bit. If the distance between the threshold value used is determined (first distance <last distance),
Add another bit equal to the preceding bit, reverse the polarity, and add more I2 columns to fill the unknown bit, otherwise
Invert the polarity directly with respect to the remaining unknown bits, add more I2 columns to fill the unknown bits, and insert and complete a single data bit End Odd number of unknown bits:
Test whether the sequence is non-polar (ie, whether an even number of I2s fits) whether the preceding (known) bit and the following (known) bit have equal data values If both questions have the same answer,
Add another bit equal to the preceding (known) bit, reverse the polarity, add more I2 columns to fill the unknown bit, and the last unknown bit to the following (known) bit Otherwise
Invert the polarity directly with respect to the previous (known) bit and add more I2 columns to fill the unknown bit. Termination Experiments have shown that such an approach has a bit error rate of 4 · 10 ⁻⁴ (or Furthermore, if some optimization of the applied threshold is used, it is possible to lead to 8 · 10 ⁻⁵ ). In contrast, a single threshold detector results in a bit error rate of about 0.1. Thus, significantly improved performance can be achieved with the bit detector and thus the entire optical disc reading system.

  The detected data bits are supplied to the RLU 205 which then determines the reference level used by the Viterbi processor 201.

  Further, the RLU 205 may comprise means for determining the first and / or second threshold utilized by the threshold detector 403 in some embodiments. For example, for the example of a 30 Gbyte Blu-ray disc in FIG. 6, the RLU 205 may determine the reference level for all states, and the upper threshold used by the threshold detector 403 is determined for state 11. For example, it may be determined as a value 10% lower than the reference level. A similar technique may be used for the lower threshold.

  Since the reference level is determined based on the detected bit, the threshold detector 403 and the RLU 205 form a closed loop system. However, experiments have shown that a stable, reliable and fast initialization is possible even without any prior knowledge of the reference level. FIG. 8 shows an example of how quickly the reference level reaches an accurate value, starting from an initial state of zero.

  Although the above discussion has focused on a fixed minimum run length, the minimum run length may be variable and dynamic in some embodiments, and may be described in particular by a function or algorithm. For example, the minimum run length is of length N for several iterations and may change to M after a certain number of iterations of length N run lengths.

  It will be understood that the foregoing description has described embodiments of the invention in connection with various functional units and processors for the sake of clarity. However, it will be apparent that any suitable distribution of functionality between the various functional units or processors may be utilized without departing from the invention. For example, functionality described to be performed by separate processors or controllers may be performed by the same processor or controller. Thus, a reference to a particular functional unit should not be considered a strict logical or physical structure, but merely be considered as a reference to a suitable means for providing the described function.

  The invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements of an embodiment of the invention may be implemented in any suitable manner physically, functionally and logically. A function may be implemented by a single unit, may be implemented by a plurality of units, or may be implemented as part of another functional unit. The present invention may be implemented in a single unit or may be physically and functionally distributed between various units and processors.

  Although the invention has been described in connection with some embodiments, it is not intended that the invention be limited to the specific form disclosed herein. The scope of the invention is limited only by the appended claims. In addition, while features have been described in connection with particular embodiments, those skilled in the art will appreciate that the various features of the described embodiments may be combined in accordance with the present invention. In the claims, the word “comprise” does not exclude the presence of other elements or steps.

  In addition, multiple means, elements or method steps may be listed separately or may be implemented by, for example, a single unit or processor. In addition, although individual features may be included in different claims, the features may be advantageously combined and may be included in different claims because a combination of these features is not available and / or It does not mean that it is not advantageous. The inclusion of a feature in a certain category of claims does not imply a limitation on that category, but indicates that the feature is equally applicable to other claim categories as appropriate. Further, the order of features in the claims does not indicate the order in which these features operate, and in particular, the order of the individual steps in a method claim requires that the steps be performed in that order. It does not indicate. These steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Accordingly, references to “a” (an), “first”, “second”, etc. do not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

1 illustrates an example of an optical disk reader according to some embodiments of the present invention. 2 illustrates an example of a Viterbi detector according to some embodiments of the present invention. An example of a reference level unit is shown. 2 illustrates an example of a bit detector according to some embodiments of the present invention. An example of a central aperture signal for a 30 Gbyte Blu-ray disc is shown. An example of reference level values for a 30-Gbyte Blu-ray disc is shown. An example of a central aperture signal for a 30 Gbyte Blu-ray disc is shown. An example of a reference level value for a 30 GB Blu-ray disc is shown.

Claims (13)

A bit detector for an optical disk reader,
Means for receiving a central aperture signal value from an optical disc reader;
Assigning a first data value to a data bit having a corresponding central aperture signal value above a first threshold and assigning a second data value to a data bit having a corresponding central aperture signal value below a second threshold A first means of
For at least one data bit of a sequence of data bits having a corresponding central aperture signal value between the first threshold and the second threshold, adjacent to the run-length encoding of these data bits and the sequence Second means for assigning a data value in response to the data value of the at least one data bit;
A bit detector.   The second means is configured to divide the sequence into several minimum run length subsets and a remaining subset having several remaining data bits, the data bits in each of the subsets being identical The bit detector of claim 1, wherein the data values are assigned and successive subsets in the sequence are assigned opposite data values. The second means includes
From the first central aperture signal value of the first data bit of the sequence to the threshold closer to the central aperture signal value of the preceding data bit preceding the first data bit of the first and second thresholds Determine an indication of the first distance,
From the second central aperture signal value of the last data bit of the series to the threshold value closer to the central aperture signal value of the data bit following the last data bit of the first and second threshold values. Determine the suggestion of the distance of two,
3. The apparatus according to claim 2, configured to determine the position of the remaining subset at the beginning or end of the sequence in response to a comparison of the first distance suggestion and the second distance suggestion. The described bit detector.   4. The bit of claim 3, wherein the second means is configured to assign to the remaining subset a data value corresponding to a data value assigned to an adjacent data bit outside the sequence. Detector. The second means sets the data value of the first subset of the series to a data value opposite to the preceding data value of the data bit immediately before the series,
The remaining subset is empty;
3. The bit detector according to claim 2, configured to be set when the preceding data value is different from a data value of a data bit immediately after the sequence and the number of subsets in the sequence is an even number. . The second means sets the data value of the first subset of the series to a data value opposite to the preceding data value of the data bit immediately before the series,
The remaining subset is empty;
The bit according to claim 2, configured to be set when the preceding data value is the same as the data value of a data bit immediately after the sequence and the number of subsets in the sequence is an odd number. Detector. The second means divides the subset into a first subset located at the beginning of the sequence and a final subset located at the end of the sequence, and sets the same data value as the preceding data value of the data bits immediately before the sequence. In the first subset, and in the final subset, the same data value as the subsequent data value of the data bits immediately after the sequence,
The remaining subset is empty;
3. The bit detector according to claim 2, wherein the bit detector is configured to be assigned when the preceding data value is different from a data value of a data bit immediately after the sequence and the number of subsets in the sequence is an odd number. The second means divides the subset into a first subset located at the beginning of the sequence and a final subset located at the end of the sequence, and sets the same data value as the preceding data value of the data bits immediately before the sequence. In the first subset, and in the final subset, the same data value as the subsequent data value of the data bits immediately after the sequence,
The remaining subset is empty;
Bit detection according to claim 2, configured to allocate when the preceding data value is identical to the data value of the data bits immediately after the sequence and the number of subsets in the sequence is an even number. vessel.   The bit detector of claim 1, wherein the first threshold and the second threshold are such that the probability of assigning an inaccurate data value is below the threshold.   The first threshold and the second threshold are such that a run length longer than the minimum run length of the run length code does not correspond to a central aperture signal value between the first threshold and the second threshold. The bit detector according to claim 1, wherein A disk reader for generating a first signal by reading the optical disk;
A bit detector for an optical disk reader;
An optical disk reading device having the bit detector,
Means for receiving a central aperture signal value from the optical disk reader;
Assigning a first data value to a data bit having a corresponding central aperture signal value above a first threshold and assigning a second data value to a data bit having a corresponding central aperture signal value below a second threshold A first means of
For at least one data bit of a sequence of data values having a corresponding central aperture signal value between the first threshold and the second threshold, run-length encoding of these data bits and adjacent to the sequence Second means for assigning a data value in response to the data value of the at least one data bit;
An optical disk reading device comprising:   The optical disk reading device according to claim 11, further comprising a reference level unit configured to determine the first threshold in response to bit detection by the bit detector. Receiving a central aperture signal value from an optical disc reader;
Assigning a first data value to a data bit having a corresponding central aperture signal value above a first threshold and assigning a second data value to a data bit having a corresponding central aperture signal value below a second threshold When,
For at least one data bit of a sequence of data values having a corresponding central aperture signal value between the first threshold and the second threshold, run-length encoding of these data bits and adjacent to the sequence Assigning a data value in response to the data value of at least one data bit to be
A method for detecting a bit value.

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